Balanced airscrew blade



Dec. 5, 1944.

A. o. DANIELS ET m. ,364,131

BALANCED AIRscR'Ew BLADE Filed Sept. 5, 1942 Z'Sheets-Sheet l l/ 4 1 502 A X INVENTORS-I ALBERT O. DANIELS HENRY V. GERMAN ATTORNEY Dec. 5, 1944. A, o. DANIELS. ETAL 2,364,131

B LANCED-AIRSGRE'W BLADE Filed Sept. 5, 1942 2 Sheets-Sheet 2 INVENTORS.

ALBERT o. DANIELS HENRY V. GERMAN ATTORNEY Patented Dec. 5, 1944 OFFICE BALANQEDAIRSCREW BLADE Albert Oliver Daniels, Chesham, Bucks, and Henry Victor German, Howgate, Bembridge, Isle t Wight, England, assignors to Hordern-Richmond Limited, Haddenham;Buckinghamshire,

England, a company of Great Brita Application September 5, 1942, Serial No. 457,504 InGreatBritain October 17, 1941 i 2 Claims. (01.170-l59) This inventionrelates to the balancing of individual blades of airscrews, andthe liked It is of course appreciated that individual blades of airscrews and the like, particularly those designed to operate at high speeds haveto be carefully balanced statically both horizontally and vertically and mustfalso be balanced namically and aerodynamically.

It is known to adjust for vertical balance by making small alterations to aerofoil sections but this is detrimental to aerodynamic balance, The empirical method of adding .weights to the root end is also known but this alters the mass weightof the blade thereby affecting the horil J i it .15

zontal balance. 1 u

u The object of the present invention is to provide means for effecting vertical balance of individual airscrew blades statically, withoutthe above-mentioned disadvantages. l

The present invention consists in the provision at or in the base or rootendof ablade of two or morefmoment masses which may be oi equal moment; adjustable about a common centre situated on the axis of the blade root or centrezline of adaptation of blade to hub. The moment masses may be in adjacent planes so as'to be movable one overthe other or may be in the same plane. The masses of two equal moment masses j would be in balance when diametrically opposed or with more than two moment masses of equal metrically arranged. By rotatingthese moment massesabout their common centre any degree of obtained when the moment masses are set so that so moment these would be in .balance when syrm l the meanfmoments of all are directly in line and on.the same side of the centre, in the case of moment masses which are arranged insuperimposed planes. In the case of moment masses arranged in the same plane the maximummoment will be obtained when themoment masses aretouching oneanother.

The moment masses maybe mounted on a central support or-by peripheral location and may be within or on the root end and in either case a centrally disposed adjustable or variable mass may be provided for adjustment of horizontal balance, for instance, a centraltube may be provided, within which may be placed a balance weight which may be adjustable axially of said tube.

It will be realised that the form of these moment masses may be varied to suit diiferent designs of blade root and may consist of superimposed or of concentrically disposed eccentric masses. 9 m

Whilst two equal moment masses .of suitable moment can be adjustedto correct any amount of vertical out of balance there may be occasions where it is known that the average blade of any one type when finished is always out of vertical balance in one direction due, for example, to the presence of a metal leading edge or the type of covering used. ;In such a caseithe use of a third moment mass positioned to correct the average known errorwould enable the two remaining equal moment masses tobe used for fine adjustment of the balance. l

"Where the diameter of the space available for positioning the said momentmasses is limited the desired moment may be obtained by coupling together two or moresets of moment masses to be operable in unison in .the manner employed in coupling together the vanes of a variable electric condenser, such as is used in the tuning circuit of a wireless receiver.

Reference will now be made to the drawings jfiled herewith, wherein,

according to the invention also adjusted to cormet the error shown in Fig. 1.

Fig. 4 is an endview of the root end shown in Fig. 3. a

In Fig. 1 it has been ascertained that the airscrew blade under test is out of balance vertically to the extent of 4" oz., in the direction of the ordinate OA and 3" oz. in the direction of the abscissa OB. The resultant of these two forces is represented by the line OX.

Referring now to Fig. 2 the two moment masses C andl D are adjustably mounted in superposed relation in the root end E about a central axis 0. It will be seen that each moment mass is formed by removing a semi-circular shaped portion from a solid disc. Therimlike portion left surrounding the hollow from which a part of the mass has been removed serves as a support for the complementary moment mass and maintains their relative axial position in the root end irrespective of the angular position.

The two cams C and D shown in Fig. 2 have been .turned so that they overlap in the left hand bottom area and the centre line OX of the overthexinterion oftherootend.

lapping portion is parallel to the resultant OX in- Fig. 1. By adjusting the amount of overlap whilst retaining the direction of the centre line OX of the overlapping portion the resultant force axially in the root end E but are disposed within the root end E no alteration of the-horizontal;

balance takes place and the dynamic balance'is not affected. 1

In the form shown in Fig."2 it wilr'benoted that the central support 'for' the ;two.moment.

masses consists of a tube Fimwhichi anzaxially larly with respect to each other and, for example, may be set and secured in the position shown in Fig. 4 to provide a mass moment for correctin an out of balance similar to that shown in Figs.

1 and 2.

Di's'pos'ed within theisleeve il iarea number 'oflead discs 24 carried on a threaded rod 25 having a head 26 the lead discs being clamped *a'gainst the head 26 by a plate 21 and nuts 28.

adjustable mass may be disposed for'the" purpose of effecting horizontal balance.

In order to avoid or correct any couplel formed by said moment masses being in a difierent plane.

of rotation to that of the airscrew being'bala'nc'ed" the moment masses mayrberduplicated so; as. tobe arranged in complementary pairs for suitable adju'stment by :which the 1 iavoi dance or' correction of anyrcouplemay.beefiected:

. Referring mow to the modified construction :the/llinei3-3 of :Fig. .4 looking in the direction .of the :arrowstheroot end lfl is bored longitudixnally :to- -:receive ar sleeve WI 1 -.closed at the inner end, the bottom.ofithetborevbeing. hemispherical.

Y.Therinner end ofxsleeve l lis- :provided with a small; aperture 1 l2 1 to spermitnof :the escape of air aslthe: sleevezisiforcedi into the. bore. The sleeve H is a close fit withimt-hemore andbeforein- -sertion zthe bore is coated with :a -suitab-le adhe- .sive. :After': the sleeve l I-- has been iinserted the aperture 12. is: closedeandlsealedin any convenient way: to Eprevent moisture. from {gaining access .to

.The open end: ofthe sleeve l I is threaded on zthez'outside to receiveia=nut= l 3-.-and on-the. inside to receive a plug M the two :threads ,being tof :opposi-te sense. Thewsleeve-ll isformed-with a shoulder l5 near the outer-:endhavirrgachamfer which is adapted to contactthe. root: end lllvand act as: a stop to ,limit the insertion. of the sleeve. .The root end all] i i vshown seeuredtin a socket :l 6

provided in t-theausual manner with threads l 1.

Mounted on the root end l0 within the socket. t6

.iand surrounding .--the-=sleeve ll I .is .a ,plate 18 .;se-

.cured by three screws 2 l 9 and. having ;a .band..of

.radialserrationsdll-.disposedtnear the periphery. Conveniently the number ;-of .said-Jadial serrationsanay be.360. i H

The nut I3 is'formed with a flange Zl which .serves as a'retainingfiange. Twomoment masses r22 -and ..23 respectively. are mounted. within .the socket Hi .and :are located-om the-periphery of the .nut t3 being heldipressed against the serrations QZO by flange ZI .ofthe-nutl 3. The moment cams 22 and 23 are formed with corresponding radial .serrationsto engage the radial; serrations .20.

-It will.be seen-that onloosening the/nut I'3the moment. masse 22 .and "23 can. be .moved anguthe plug'l'l "which serves to keep the head 26 i'pressed agaihstit'he: elosed inner end of the sleeve ingt individual a-airserew blades to t to be under :stood /that theminvention cansbe-applied to the balancing ,-of anyJQrm: ofl individual b1ade..for-a -propelle fanor: the like all of which are to vbe regarded -asr include'dtin-the expression airscrew blade.

What we claim'and desire to secure by Letters Patentsis:

1. In.combinationwitdthel root. endof. a...bla'de, .a-cylindrical .sleevesecurediin .a longitudinaLbore vof the root en'd of l the lblade and exteriorly threaded at; the-outer .endla socket secured .to said root end and extending longitudinally thereof. and projectingbeyondthe same, .a stationary annular. .plate iarrange'dww'ithin the .socket and surrounding saidsleeve and. provided with. radial serrations, a plurality ot segmental moment masses arranged v withimsaid .socket and. adjustable around the..sleeve. and ..provided .with' radial -serrations engaging serrations of said vplate, .an'd a nut .r'nountedlpmthe threaded .end of the sleeve and engaging the. moment masses and maintaining the serrations thereof in engagement with serrations translate- .2'.J1ncombin tiomWithCthe-root.erfddf a blade, a.cylindrical.sleeve. secured in .a longitudinatbore .oi .th vro t-.er1d.Iof .the..bla'de .and exteriorly threaded at fits'.oute1:.end,;a socket secured to said root end. .and extending longitudinally. 1. thereof v.beyorid the. same a stationary annular. plate. .ar-

ranged .withintlthe. socket and surrounding said sleeve, and .provided withuradial serrations, .a nut mountedon the threaded Iend ot 'the. sleeve and rovided Twithfa laterally projectin "retaining fiange,l and .1a jpluralit'yi of Zsegmentalj moment masses mounted .within thesocket and locatedlo'n v and ladjustable around the Tperiphery 6f the nut .and,iprovide'd with radial serrationsIengaging'serrations. of .said'plate'f d maintained in suchtn- ,.gag'ement b'ythe retaim giflan'ge or the. nut.

A'LBER OEIVEHDANIEL'S. HENRY VICTOR'GERMAN.

-'I'he-..end-.of the threaded rod 25 is located in 

